Metals passivation

ABSTRACT

A zeolite-containing catalytic cracking catalyst having been passivated by treatment with an aqueous solution which has been prepared by mixing an antimony oxide, ammonium bifluoride and water, at an atomic ratio of F:Sb in excess of about 6:1, is used in a process for catalytically cracking a hydrocarbon-containing feed, in particular one which contains metal impurities. In one embodiment, the above-described aqueous solution is injected into the feed. In other embodiments, the solution is injected into the cracking zone or into a catalyst regeneration zone.

This is a divisional application of copending application Ser. No.504,778, filed Apr. 4, 1990.

BACKGROUND OF THE INVENTION

This invention relates to a process for treating a zeolite-containingcracking catalyst with an aqueous solution comprising an antimonycompound so as to make the catalyst more resistant to the detrimentaleffects of metal poisons deposited thereon during catalytic cracking ofhydrocarbon-containing oils. In another aspect, this invention relatesto zeolite-containing cracking catalyst having been impregnated with anaqueous solution comprising an antimony compound. In a further aspect,this invention relates to a process for catalytically cracking ahydrocarbon-containing oil which contains metal impurities, wherein anaqueous solution comprising an antimony compound, is injected into theoil feed or, alternatively, into the cracking zone. In still anotheraspect, this invention relates to a process comprising catalyticallycracking a metal-contaminated hydrocarbon-containing oil, separatingcracked products from spent catalyst, and regenerating the spentcatalyst for recycle to the catalytic cracking zone, wherein an aqueoussolution comprising an antimony compound is injected into a catalystregeneration zone.

It is well known to use antimony compounds as passivating agents forzeolite-containing cracking catalysts so as to mitigate the detrimentaleffects of metal poisons (primarily nickel/vanadium compounds) depositedthereon. Some of these antimony compounds are water soluble, such asthose disclosed in U.S. Pat. Nos. 3,711,422; 4,595,771; 4,595,772 and4,609,747. It is frequently more practical to employ an aqueous solutionof an antimony compound as passivating agent rather than a solution ofan antimony compound in a flammable organic solvent, especially if thepassivating agent is to be injected into a hot oxidative catalystregeneration zone. The use of aqueous solution essentially eliminatesthe danger of an explosion which exists when a highly flammable solutionis used. The present invention is directed to the use of an aqueoussolution comprising an antimony compound which is more effective thanknown aqueous antimony-containing metal passivating agents. The term"metals passivating", as used herein, implies that the detrimentaleffects during catalytic cracking (in particular excessive hydrogengeneration and/or lower gasoline yields) caused by metal deposits (suchas compounds of Ni, V and Cu) on a cracking catalyst composition havebeen mitigated.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a process for passivating acatalytic cracking catalyst composition. It is another object of thisinvention to provide a passivated catalytic cracking catalystcomposition. It is a further object of this invention to provide acatalytic cracking process employing a passivated catalytic crackingcatalyst composition. It is still another object of this invention toemploy an aqueous passivating agent in a catalytic cracking process.Other objects and advantages will become apparent from the detaileddisclosure and the appended claims.

In accordance with this invention, a zeolite-containing crackingcatalyst composition is contacted (treated) with an aqueous solutionprepared by mixing an antimony oxide (preferably Sb₂ O₃), ammoniumbifluoride (NH₄ HF₂) and water, followed by substantially drying thethus-contacted catalyst composition. The atomic ratio of F:Sb in thesolution can be varied over a wide range.

In one mode of operation, a fresh zeolite-containing catalytic crackingcatalyst composition is contacted (treated) with the aqueous solutiondescribed above. In another mode of operation, a regenerated, used(spent), metal-contaminated spent zeolite-containing catalytic crackingcatalyst is contacted with the aqueous solution described above. In afurther mode of operation, a mixture of a fresh zeolite-containingcatalytic cracking catalyst composition and a regenerated, used (spent)metal-contaminated zeolite-containing cracking catalyst composition iscontacted with the aqueous solution described above.

Also in accordance with this invention, there is provided azeolite-containing catalytic cracking catalyst having been contacted(treated) with the aqueous solution described above (by either one ofthe three contacting modes).

Further in accordance with this invention, a process for catalyticallycracking a hydrocarbon-containing feed, particularly one which containsmetal impurities, comprises contacting said feed under catalyticcracking conditions, substantially in the absence of added freehydrogen, with a catalytic cracking catalyst composition having beencontacted (treated) with the aqueous solution described above (by eitherone of the three contacting modes).

Still further in accordance with this invention, a process forcatalytically cracking a hydrocarbon-containing feed, particularly onewhich contains metal impurities, in the presence of a zeolite-containingcracking catalyst, substantially in the absence of added free hydrogen,comprises injecting the aqueous solution described above into the feedor, alternatively, into the catalytic cracking zone.

Additionally in accordance with this invention, there is provided acombination process comprising catalytically cracking (substantially inthe absence of added free hydrogen) a hydrocarbon-containing feed (asdescribed above), separating liquid and gaseous cracked products fromthe spent (used) zeolite-containing catalytic cracking catalyst,stripping adhered hydrocarbons from the thus-separated spent catalyticcracking catalyst, heating the stripped spent catalytic crackingcatalyst in a regeneration zone with a free oxygen containing gas (so asto burn off coke deposits), and recycling at least a portion of theregenerated catalytic cracking catalyst to the cracking zone; whereinthe aqueous solution described above is injected either directly intothe regeneration zone or, alternatively, into a conduit leading to orfrom the regeneration zone, so as to deposit the solute contained in theaqueous solution (described above) onto the spent cracking catalyst.

DETAILED DESCRIPTION OF THE INVENTION

The term "catalytic cracking", as used herein, implies that essentiallyno hydrocracking occurs and that the catalytic cracking process iscarried out with a hydrocarbon-containing oil feed substantially in theabsence of added hydrogen gas, under such conditions as to obtain atleast one liquid product stream having a higher API gravity (measured at60° F.) than the feed. The term "spent", as used herein, implies that atleast a portion of the zeolite-containing cracking catalyst compositionhas been used in a process for catalytically crackinghydrocarbon-containing oils, in particular those containing metal (Ni,V, Cu) impurities, and has then been regenerated by stripping adheredoil from the catalyst composition (such as by steam-stripping) andsubsequent heating in an oxidizing gas atmosphere (such as air) so as toburn off coke deposits on the catalytic cracking catalyst composition.

The aqueous solution used in the processes of this invention can beprepared by mixing, in any order, water, an antimony oxide (Sb₂ O₃ orSb₂ O₅ or the like or combinations thereof, preferably Sb₂ O₃) andammonium bifluoride (NH₄ HF₂) in such proportions as to obtain asubstantially clear solution. It is also possible to use NH₄ F and HF atan approximately equimolar ratio in lieu of NH₄ HF₂. It is also withinthe scope of the invention (yet presently not preferred) to have minoramounts of undissolved, dispersed antimony oxide present in thesolution. Generally, the atomic ratio of F to Sb in the solution is inthe range of from about 6:1 to about 30:1. But preferably, this atomicratio exceeds about 6:1, and more preferably is in the range of fromabout 7:1 to about 25:1. The fluoride and antimony components in thesolution can be present in the solution in any suitable concentration.Generally, the antimony concentration in the solution is in the range offrom about 3 to about 30 weight-% Sb, and preferably is about 5-20weight-% Sb.

Any zeolite-containing catalytic cracking catalyst can be used in theprocesses of this invention. The zeolite component of the spentzeolite-containing cracking composition of this invention can be anynatural or synthetic crystalline aluminosilicate zeolite which exhibitscracking activity. Non-limiting examples of such zeolites are faujasite,chabazite, mordenite, offretite, erionite, Zeolon, zeolite X, zeolite Y,zeolite L, zeolite ZSM-4, zeolite ZSM-5, zeolite ZSM-11, zeolite ZSM-12,zeolite ZSM-23, zeolite ZSM-35, zeolite ZSM-38, zeolite ZSM-48, and thelike, and mixtures thereof. Additional examples of suitable zeolites arelisted in U.S. Pat. No. 4,158,621. The term "zeolite", as used herein,includes zeolites which have been pretreated, such as those from which aportion of Al has been removed from the crystalline framework, andzeolites which have been ion-exchanged with rare earth metal or ammoniumor by other conventional ion-exchange methods. The term "zeolite", asused herein, also includes essentially aluminum-free silica polymorphs,such as silicalite, chromia silicates, ferrosilicates, borosilicates,and the like, as disclosed in U.S. Pat. No. 4,556,749.

Generally, the zeolite component of the catalytic cracking catalystcomposition is dispersed in a suitable solid refractory inorganic matrixmaterial, such as alumina, silica, silica-alumina (presently preferred),aluminum phosphate, magnesium oxide, mixtures of two or more of theabove-listed materials, and the like. The preparation of suchzeolite/matrix cracking catalyst compositions is well known and is not acritical feature of this invention. Generally, the surface area(measured by nitrogen adsorption, substantially in accordance with theBET method of Brunauer, Emmett and Teller) of the zeolite/matrixcracking catalyst composition is in the range of from about 100 to about800 m² /g. Generally, the weight ratio of zeolite to matrix material inthe catalytic cracking catalyst composition is in the range of fromabout 1:20 to about 1:1.

The catalytic cracking catalyst composition used in the processes ofthis invention can be fresh (unused) or can be spent. Any spentzeolite-containing catalytic cracking catalyst composition, whichcontains at least one metal contaminant (i.e., at least one compound ofNi and/or V and/or Cu) and at least a portion of which has previouslybeen used in a catalytic cracking process and has been oxidativelyregenerated, can be used. The catalytic cracking catalyst compositioncan contain any portion of such regenerated spent catalyst composition,ranging from 100% to about 10 weight-% (i.e., containing 0% to about 90weight-% fresh, unused zeolite-containing cracking catalystcomposition). Equilibrium cracking catalysts, which are commonlyemployed in commercial catalytic cracking operations and generallycomprise a physical blend of regenerated, used (spent) cracking catalystcomposition and fresh (unused) catalytic cracking catalyst composition,are particularly suited for the processes of this invention. Anequilibrium catalyst generally comprises a mixture of catalyst particlesof various ages, i.e., a portion of the equilibrium catalyst particleshas passed through a varying number of cracking and regeneration cycles,while a small portion of the equilibrium catalyst particles is fresh(unused) catalytic cracking catalyst composition.

The contacting of the zeolite-containing catalytic cracking catalystcomposition and the aqueous solution prepared from antimony oxide andNH₄ HF₂ (described above) can be carried out in any suitable manner. Itcan be done in a vessel, preferably with agitation. Or it can be donecontinuously, such as by passing the aqueous solution through a columnfilled with a cracking catalyst composition. Or the aqueous solution canbe sprayed onto the catalytic cracking catalyst composition.

Any suitable time of contact between solution and the cracking catalystcomposition can be employed, generally from about 0.1 to about 5 hours.Any suitable temperature can be employed in the contacting step,generally from about 10° C. to about 300° C. (preferably about 60°-90°C.), generally at ambient pressure (1 atm). The weight ratio of theaqueous solution (described above) to the zeolite-containing catalyticcracking catalyst composition is generally chosen so as to provide atreated catalyst composition possessing a level of about 10 ppm Sb(parts by weight Sb per million parts by weight catalyst) to about 5weight-% Sb, preferably about 0.1-2 weight-% Sb, based on the weight ofdry catalyst composition. Generally, the fluoride content in the treatedcatalyst composition is such as to provide an atomic ratio of F:Sb inthe catalyst of from about 6:1 to about 30:1. Preferably, this ratioexceeds about 6:1. More preferably, this ratio is about 7:1 to about25:1, most preferably about 10:1 to about 15:1.

The thus-treated catalytic cracking catalyst composition (now containingSb and F) is dried, preferably at about 80°-120° C. for about 0.5-10hours. Generally, the water content in the substantially dried catalystcomposition is less than about 5 weight-% H₂ O (preferably less than 2weight-% H₂ O). If the contacting of the catalytic cracking catalystcomposition with the aqueous solution is carried out with a hot catalystcomposition (e.g., one which is present in or exits from the oxidativeregenerator of a catalytic cracking unit), a separate drying step can beomitted, because the drying occurs in the contacting zone containing thehot catalyst. Thus, it is within the scope of this invention to have thecontacting and drying steps occur substantially simultaneously.Optionally, the substantially dried, treated catalytic crackingcomposition can be calcined at a higher temperature (i.e., above 200°C.); however, this calcining step generally is not needed.

The catalytic cracking catalyst composition which has been contactedwith the aqueous solution (prepared from antimony oxide and ammoniumbifluoride) can be used in any catalytic cracking process, i.e., aprocess for catalytically cracking hydrocarbon-containing oilfeedstocks, in any suitable cracking reactor (e.g., in a FCC reactor orin a Thermofor moving bed reactor), essentially in the absence of addedhydrogen gas. The treated catalyst composition can be used alone or inadmixture with fresh (unused) zeolite-containing catalyst composition incatalytic cracking processes.

The hydrocarbon-containing feed stream for the catalytic crackingprocess of this invention can be any suitable feedstock. Generally thefeed has an initial boiling point (ASTM D1160) in excess of about 400°F., preferably a boiling range of from about 400° to about 1200° F.,more preferably a range of from about 500° to about 1100° F., measuredat atmospheric pressure conditions and contains metal impurities. TheAPI gravity (measured at 60° F.) generally is in the range of from about5 to about 40, preferably from about 10 to about 35. Generally, thesefeedstocks contain Ramsbottom carbon residue (ASTM D524; usually about0.1-20 weight-%), sulfur (generally about 0.1-5 weight-% S), nitrogen(generally about 0.05-2 weight-% N), nickel (generally about 0.05-30 ppmNi, i.e., parts by weight of Ni per million parts by weight of feed),vanadium (generally about 0.1-50 ppm V) and copper (generally about0.01-30 ppm Cu). Non-limiting examples of suitable feedstocks are lightgas oils, heavy gas oils, vacuum gas oils, cracker recycle oils (cycleoils), residua (such as distillation bottoms fractions), andhydrotreated residua (e.g., hydrotreated in the presence of Ni, Co,Mo-promoted alumina catalysts), liquid coal pyrolyzates, liquid productsfrom extraction or pyrolysis of tar sand, shale oils, heavy fractions ofshale oils, and the like. The presently most preferred feedstocks areheavy gas oils and hydrotreated residua.

Any suitable reactor can be used for the catalytic cracking process ofthis invention. Generally, a fluidized-bed catalytic cracking (FCC)reactor (preferably containing one or more risers) or a moving-bedcatalytic cracking reactor (e.g., a Thermofor catalytic cracker) isemployed, preferably a FCC riser cracking unit. Examples of such FCCcracking units are described in U.S. Pat. Nos. 4,377,470 and 4,424,116.Generally a catalyst regeneration unit (for removal of coke deposits) iscombined with the FCC cracking unit, as is shown in the above-citedpatents.

Specific operating conditions of the cracking operation greatly dependon the type of feed, the type and dimensions of the cracking reactor andthe oil feed rate. Examples of operating conditions are described in theabove-cited patents and in any other publications. In an FCC operation,generally the weight ratio of catalyst composition to oil feed (i.e.,hydrocarbon-containing feed) ranges from about 2:1 to about 10:1, thecontact time between oil feed and catalyst is in the range of from about0.2 to about 2.0 seconds, and the cracking temperature is in the rangeof from about 800° to about 1200° F. Generally, steam is added with theoil feed to the FCC reactor so as to aid in the dispersion of the oil asdroplets. Generally, the weight ratio of steam to oil feed is in therange of from about 0.05:1 to about 0.5:1.

The separation of the thus used cracking catalyst composition fromgaseous and liquid cracked products and separation of cracking productsinto various gaseous and liquid product fractions can be carried out byany conventional separation means. The most desirable product fractionis gasoline (ASTM boiling range: about 180°-400° F.). Non-limitingexamples of such separation schemes are showing in "Petroleum Refining"by James H. Gary and Glenn E. Handwerk, Marcel Dekker, Inc., 1975.

Generally, the separated, used cracking catalysts are regenerated,preferably by steam stripping for removal of adhered oil and subsequentheating under oxidizing conditions so as to burn off carbon deposits. Atleast a portion of the regenerated cracking catalyst composition canthen be treated by the catalyst treating process of this invention,described above, and thereafter be recycled to the catalytic crackingreactor, generally in admixture with fresh (unused) cracking catalyst.

In one embodiment of this invention, the aqueous solution (prepared fromantimony oxide and ammonium bifluoride; described above) is injectedinto the hydrocarbon-containing feed stream before it enters thecatalytic cracking reactor. The amount of the injected aqueous solutionis chosen such that the cracking catalyst in the cracking zone containsabout 10 ppm to about 5 weight-% Sb (preferably about 0.1-2 weight-%Sb). In another (yet less preferred) embodiment, the aqueous solution isdirectly injected into catalytic cracking reactor.

In a particularly preferred embodiment, the aqueous solution describedabove is injected into the oxidative regenerator, so that the solutioncomes in contact with the hot spent catalyst and the solute contained inthe solution deposits on the catalyst. The aqueous solution is injectedat such a rate as to provide a level of about 10 ppm to about 5 weight-%Sb, preferably about 0.1-2 weight-% Sb, in the regenerated crackingcatalyst composition. Generally, the atomic ratio of F:Sb on thethus-treated regenerated cracking catalyst composition is in the rangeof from about 6:1 to about 30:1, but preferably exceeds about 6:1. Morepreferably, this atomic ratio is about 7:1 to about 25:1, mostpreferably about 10:1 to about 15:1. It is within the scope of thisinvention to inject the aqueous solution into a catalyst-transportingconduit leading to the regenerator or, alternatively, from theregenerator. The thus-treated regenerated catalytic cracking catalystcomposition can be recycled, optionally admixed with fresh (treated oruntreated) catalytic cracking catalyst composition, to the catalyticcracking zone.

The following examples are presented to further illustrate thisinvention and are not to be considered as unduly limiting the scope ofthis invention.

EXAMPLE I

This example illustrates the preparation of the aqueous passivatingagent of this invention and its use for treating a used catalyticcracking catalyst composition which contains metal deposits.

About 14.2 g (0.25 mole) NH₄ HF₂ (ammonium bifluoride; provided byMallinckrodt, Inc., St. Louis, Mo.) was dissolved in about 40 cc water.To the aqueous solution was added, with heating and stirring for about20 minutes, about 12.0 g (0.041 mole) Sb₂ O₃. The slightly turbidsolution was filtered through a coarse frit. The atomic ratio of F:Sb inthis solution, labeled Solution A, was about 6:1.

Another solution, labeled Solution B, was prepared as described forSolution A, except that 28.4 g (0.5 mole) NH₄ HF₂ and 65 cc water wasused. Thus, the atomic ratio of F:Sb in Solution B was about 12:1. ThepH of this solution was 6.

The above-described solutions were used to treat a zeolite-containingequilibrium catalytic cracking composition which was a blend of freshcracking catalyst and of spent cracking catalyst (having been used andregenerated in a FCC cracking operation at a refinery of PhillipsPetroleum Company). The equilibrium catalyst composition (labeled"J-8802") contained about 25 weight-% zeolite, which was embedded in asilica-alumina matrix, 0.18 weight-% Ni, 0.32 weight-% V, 0.53 weight-%Fe, 0.01 weight-% Cu, 0.06 weight-% Sb, and 0.34 weight-% Na. "J-8802"had a surface area of about 110 m² /g, a total pore volume of 0.18 cc/g,an apparent bulk density of 0.90 g/cc, and a zeolite unit cell size of24.34 Å.

50 grams of catalyst composition "J-8802" was impregnated with 0.25 g ofSolution A (diluted with 25 cc water). The thus-treated catalystcomposition was dried at about 250° C. and calcined in air for 1 hour atabout 1250° F. The thus-treated catalyst material contained about 1000ppm Sb.

Another 50 gram sample of "J-8802" was impregnated with 0.33 g ofSolution B (diluted with 25 cc water), dried and calcined, as describedabove. Again, the thus-treated catalyst material contained about 1000ppm Sb.

A third 50 g sample of "J-8802" was impregnated with a mixture of 163 ccwater and 0.155 g Phil-Ad CA 6000 (an aqueous dispersions of Sb₂ O₅,containing 22 weight-% Sb, marketed by Phillips Petroleum Company,Bartlesville), dried and calcined, as described above. The thus-treatedcatalyst material contained 1000 ppm Sb.

Finally, a sample of "J-8802" was impregnated with an aqueous solutionof antimony tartrate, dried and calcined (as described above), at suchconditions as to give an antimony level of 5000 ppm Sb.

EXAMPLE II

This example illustrates the performance of the antimony-treatedcracking catalysts described in Example I in a catalytic cracking testreactor.

The test reactor was a MCBU (micro-confined bed unit) cracking testreactor, substantially in accordance with the procedure of Example II ofU.S. Pat. No. 4,794,095. Cracking test conditions comprised atemperature of about 950° F., a catalyst to oil weight ratio of 6:1, andthe use of a hydrotreated residuum as oil feed having API gravity (at60° F.) of 18.7, sulfur content of 0.53 weight-%, basic nitrogen contentof 0.09 weight-%, Conradson carbon content of 6.07 weight-%, nickelcontent of 10.6 ppm and vanadium content of 12.7 ppm. Average testresults of at least two duplicate runs for each catalyst are summarizedin Table I.

                  TABLE I                                                         ______________________________________                                                           Average                                                    Treating           Conversion                                                                              Average                                                                              Average                                   Agent    ppm Sb    (Wt % of  Gasoline                                                                             Hydrogen                                  for Catalyst                                                                           on Catalyst                                                                             Feed)     Yield.sup.1)                                                                         Generation.sup.2)                         ______________________________________                                        Solution A                                                                             1000      75.3      50.3   293                                       (6:1 Ratio                                                                    of F:Sb)                                                                      Solution B                                                                             1000      76.7      50.3   319                                       (12:1 Ratio                                                                   of F:Sb)                                                                      Phil-Ad 6000                                                                           1000      75.5      50.0   337                                       Sb Tartrate                                                                            5000      76.5      50.5   305                                       in H.sub.2 O                                                                  None       0       74.0      48.0   395                                       ______________________________________                                         .sup.1) weight % of converted feed                                            .sup.2) standard cubic feet H.sub.2 per barrel of converted feed.        

Test results in Table I clearly show the advantage of Solutions A and B,prepared by dissolving Sb₂ O₃ and NH₄ HF₂ in water, as passivating agentover an aqueous dispersion of Sb₂ O₅ and an aqueous solution of Sbtartrate:lower H₂ generation at equivalent Sb loading. As is shownabove, the Sb tartrate treated catalyst material contained five timesmore Sb than the catalyst material which had been treated with SolutionsA and B. Treatment with Solution B (12:1 atomic ratio of F:Sb) resultedin a higher conversion than treatment with Solution A (6:1 atomic ratioof F:Sb). Thus, it is presently preferred to employ solution having aF:Sb atomic ratio in excess of about 6:1.

Attempts to prepare stable solutions of SbF₃ in water were notsuccessful because SbF₃ hydrolyzed and formed a precipitate (probablySbOF or hydrated antimony oxide).

Reasonable variations, modifications and adaptations for variousconditions and uses can be made within the scope of the disclosure andappended claims.

That which is claimed is:
 1. A process for catalytically cracking ahydrocarbon containing feed which contains metal impurities comprisingcontacting said feed under catalytic cracking conditions in a crackingreactor, substantially in the absence of added free hydrogen, with azeolite-containing catalytic cracking catalyst composition which hasbeen treated with an aqueous solution having been prepared by mixingantimony oxide, ammonium bifluoride and water, followed by substantiallydrying the thus-treated catalyst composition; wherein the atomic ratioof F:Sb in said aqueous solution and in said thus-treated catalystcomposition exceeds about 6:1.
 2. A process in accordance with claim 1,wherein said antimony oxide is Sb₂ O₃.
 3. A process in accordance withclaim 1, wherein said atomic ratio of F:Sb is in the range of from about7:1 to about 25:1.
 4. A process in accordance with claim 1, wherein saidantimony oxide is Sb₂ O₃, and said atomic ratio of F:Sb is in the rangeof from about 10:1 to about 15:1.
 5. A process in accordance with claim1, wherein the antimony concentration in said aqueous solution is in therange of from about 3 to about 30 weight-% Sb.
 6. A process inaccordance with claim 1, wherein said zeolite-containing catalyticcracking catalyst composition is a fresh catalyst composition.
 7. Aprocess in accordance with claim 1, wherein said zeolite-containingcatalytic cracking catalyst composition is a spent catalyst compositionwhich contains at least one metal contaminant selected from the groupconsisting of compounds of nickel, vanadium and copper.
 8. A process inaccordance with claim 1, wherein said zeolite-containing catalyticcracking catalyst composition is a mixture of (a) a fresh catalystcomposition and (b) a spent catalyst composition which contains at leastone metal contaminant selected from the group consisting of nickel,vanadium and copper.
 9. A process in accordance with claim 1, whereinsaid thus-treated catalyst composition contains about 10 ppm to about 5weight-% antimony.
 10. A process in accordance with claim 1 wherein saidfeed has an API gravity of about 5 to
 40. 11. A process in accordancewith claim 10, wherein said metal impurities are present in said feed ata level of about 0.05-10 ppm nickel and about 0.1-50 ppm vanadium.
 12. Aprocess in accordance with claim 11, wherein said feed also comprisesabout 0.01-30 ppm copper.
 13. A process in accordance with claim 1,wherein said aqueous solution has been injected into said feed.
 14. Aprocess in accordance with claim 1, wherein said aqueous solution hasbeen injected into said cracking reactor.
 15. A process in accordancewith claim 1 comprising the additional steps of separating liquid andgaseous cracked products from spent catalytic cracking catalystcomposition, stripping adhered hydrocarbons from the thus-separatedcatalytic cracking catalyst composition, heating the thus-strippedcatalytic cracking catalyst composition in a regeneration zone with afree oxygen, and recycling at least a portion of the thus-regeneratedcatalytic cracking catalyst composition to said catalytic cracking zone.16. A process in accordance with claim 15, wherein said aqueous solutionhas been injected into the said regenerating zone.
 17. A process inaccordance with claim 15, wherein said aqueous solution has beeninjected into a conduit leading to said regenerating zone.
 18. A processin accordance with claim 15, wherein said aqueous solution has beeninjected into a conduit leading from said regenerating zone.